.input-group {
  width: 400px;
  margin: 10px auto 0;
}

.input-group input {
  width: 100%;
  box-sizing: border-box;
  outline: none;
  border: 1px solid #333;
  padding: 5px 10px;
}

.student-sex {
  display: inline-block;
}

.student-sex input {
  width: 50px;
}